Navigation technology is a widely available tool in spine surgery and has become a part of clinical routine in many centers. The issue of where and when navigation technology should be used is still an issue of debate. It is the aim of this study to give an overview on the current knowledge concerning the technical capabilities of image-guided approaches and to discuss possible future directions of research and implementation of this technique. Based on a Medline search total of 1,462 publications published until October 2008 were retrieved. The abstracts were scanned manually for relevance to the topics of navigated spine surgery in the cervical spine, the thoracic spine, the lumbar spine, as well as ventral spine surgery, radiation exposure, tumor surgery and cost-effectivity in navigated spine surgery. Papers not contributing to these subjects were deleted resulting in 276 papers that were included in the analysis. Image-guided approaches have been investigated and partially implemented into clinical routine in virtually any field of spine surgery. However, the data available is mostly limited to small clinical series, case reports or retrospective studies. Only two RCTs and one metaanalysis have been retrieved. Concerning the most popular application of image-guided approaches, pedicle screw insertion, the evidence of clinical benefit in the most critical areas, e.g. the thoracic spine, is still lacking. In many other areas of spine surgery, e.g. ventral spine surgery or tumor surgery, image-guided approaches are still in an experimental stage. The technical development of image-guided techniques has reached a high level as the accuracies that can be achieved technically meet the anatomical demands. However, there is evidence that the interaction between the surgeon ('human factor') and the navigation system is a source of inaccuracy. It is concluded that more effort needs to be spend to understand this interaction.

In a prospective and randomised clinical study, acetabular cups were implanted free-hand (control group n=22) or with computer assistance using an image-free navigation system (study group n=23). The cup position was determined postoperatively on pelvic CT. An average inclination of 42.3°(range: 30°-53°; SD±7.0°) and an average anteversion of 24.0°(range: −3°to 51°; SD±15.0°) were found in the control group, and an average inclination of 45.0°(ranage: 40°-50°; SD±2.8°) and an average anteversion of 14.4°(range: 5°-25°; SS±5.0°) in the computer-assisted study group. The deviations from the desired cup position (45°inclination, 15°anteversion) were significantly lower in the computer-assisted study group (p<0.001 each). While only 11/22 of the cups in the control group were within the Lewinnek safe zone, 21/23 of the cups in the study group were placed in this target region (p=0.003).Résumé Dans un étude clinique prospective et randomisé, les cupules acétabulaires ont été implantées de façon habituelle (n=22; groupe témoin) ou avec assistance d'un ordinateur qui utilise un système de navigation imagelibre (n=23; groupe d'étude). La place de la cupule a été déterminée après l'opération sur un scanner pelvien. Une inclinaison moyenne de 42,3°(30°à 53°; ±7.0°) et une antéversion moyenne de 24,0°(−3°à 51°; ±15.0°) ont été trouvées dans le groupe témoin et une inclinaison moyenne de 45,0°(40°à 50°; ±2.8°) et une antéversion moyenne de 14,4°(5°à 25°; ±5.0°) dans le groupe de l'étude assistée par ordinateur. Les déviations par rapport à la position désirée de la cupule (45°d'inclinaison, 15°d'antéversion) étaient notablement inférieures dans le groupe de l'étude assistée par ordinateur (p<0.001 chacun). Alors que seulement 11 des 22 cupules du groupe témoin étaient dans la zone sûre de Lewinnek, 21 des 23 cupules du groupe d'étude ont été placées dans cette région cible (p=0.003).

In general, fractures are treated by reduction and fixation to restore the biomechanical function of the injured bone. These principles should be applied to elderly patients with osteoporotic fractures as well. The technique reported here is adapted to the special demands of the elderly patient, i.e., minimally invasive, support of the weakened bone by cement augmentation, bone protective screw positioning and safety due to navigation support.

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The fluoroscopy-based VectorVision navigation system shows a high feasibility of computer-guided drilling with a clear reduction of radiation exposure time and can therefore be integrated into clinical routine. The additional time needed is acceptable regarding the simultaneous reduction of radiation time.